Precautions When Grounding; Example: Insulating And Grounding An Enclosure; Controller Ground Terminals; Grounding For Ac Power Supply Units - Omron NJ501-1 Series User Manual

 Precautions when Grounding
• If the same ground is used for both the signal lines and the enclosure, isolate the channel base
(a grounded metal plate inside a control panel) with an insulating material
• To prevent influence from leakage current from other electrical devices, electrically isolate the
panel in which the Controller is housed from other devices.
• If high-frequency equipment is present, then ground not only the high-frequency equipment but
also the panel itself in which the Controller is housed.
• As shown in the following diagram, when using shielded cable for I/O wiring, connect the shield
near the Controller to the enclosure ground terminal. Follow the instructions in the Communica-
tions Unit manual for preparing shielded communications cable.
 Controller Ground Terminals
The Controller has the following two ground terminals.
Protective ground terminal: Always connected to the Controller chassis to prevent electrical shock.
Functional ground terminal: Connected to a neutral point in the noise filter to provide a ground when
power supply noise causes malfunctioning.
When the functional ground terminal is correctly grounded, it is generally effective in suppressing
power supply common noise. Occasionally, however, grounding this terminal will result in picking up
more noise, so be careful when using it.
AC side

Controller Ground Terminals

 Grounding for AC Power Supply Units
When wiring to an AC Power Supply Unit, if one power supply phase of the equipment is grounded,
always connect the grounded phase to the L2/N terminal.
L1
L2/N
NJ-series CPU Unit Hardware User's Manual (W500)
The NJ-series Controllers
are designed to be
mounted so that they are
isolated (separated) from
the mounting surface to
protect them from the
effects of noise in the
installation environment
(e.g., the control panel).

Example: Insulating and Grounding an Enclosure

Controller
Input
Common
Shielded Cable Ground
Controller side
4 Installation and Wiring
Insulating material
Channel base
Output
Common
4
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